public class

ElementReader

extends Object
implements __Delete
java.lang.Object
   ↳ com.pdftron.pdf.ElementReader

Class Overview

ElementReader can be used to parse and process content streams. ElementReader provides a convenient interface used to traverse the Element display list of a page. The display list representing graphical elements (such as text-runs, paths, images, shadings, forms, etc) is accessed using the intrinsic iterator. ElementReader automatically concatenates page contents spanning multiple streams and provides a mechanism to parse contents of sub-display lists (e.g. forms XObjects and Type3 fonts). A sample use case for ElementReader is given below: ... ElementReader reader=new ElementReader(); reader.Begin(page); for (Element element=reader.next(); element!=null;element=reader.next()) { Rect bbox; if((bbox=element.getBBox())!=null) System.out.println("Bounding Box: " + bbox.getRectangle()); switch (element.getType()) { case Element.e_path: { // Process path data... double[] data = element.getPathPoints(); break; case Element.e_text: // ... break; } } reader.End(); } For a full sample, please refer to ElementReader and ElementReaderAdv sample projects.

Summary

Public Constructors
ElementReader()
Instantiates a new element reader.
Public Methods
void begin(Obj content_stream)
Begin processing given content stream.
void begin(Obj content_stream, Obj resource_dict)
Begin processing given content stream.
void begin(Page page)
Begin processing a page.
void begin(Obj content_stream, Obj resource_dict, Context ctx)
Begin processing given content stream.
void begin(Page page, Context ctx)
Begin processing a page.
void clearChangeList()
Clear the list containing identifiers of modified graphics state attributes.
Element current()
get current page element

Note: Every call to ElementReader::Next() destroys the current Element.

void destroy()
Frees the native memory of the object.
boolean end()
Close the current display list.
void formBegin()
When the current element is a form XObject you have the option to skip form processing (by not calling FormBegin()) or to open the form stream and continue Element traversal into the form.
GSChangesIterator getChangesIterator()
Get the changes iterator.
Obj getColorSpace(String name)
Get the color space.
Obj getExtGState(String name)
Get the ext GState.
Obj getFont(String name)
Get the specified font.
Obj getPattern(String name)
Get the pattern.
Obj getShading(String name)
Get the specified shading object.
Obj getXObject(String name)
Get the specified XObject.
boolean isChanged(int gstate_attrib)
Checks if given GState attribute is changed.
Element next()
Get next page element

Note: Every call to ElementReader::Next() destroys the current Element.

void patternBegin(boolean fill_pattern, boolean reset_ctm_tfm)
A method used to spawn the sub-display list representing the tiling pattern of the current element in the ElementReader.
void patternBegin(boolean fill_pattern)
Pattern begin.
void type3FontBegin(CharData char_data, Obj resource_dict)
A method used to spawn a sub-display list representing a Type3 Font glyph.
void type3FontBegin(CharData char_data)
pawn a sub-display list representing a Type3 Font glyph.
Protected Methods
void clearList()
Clear list.
void finalize()
[Expand]
Inherited Methods
From class java.lang.Object
From interface com.pdftron.pdf.__Delete

Public Constructors

public ElementReader ()

Instantiates a new element reader.

Public Methods

public void begin (Obj content_stream)

Begin processing given content stream. The content stream may be a Form XObject, Type3 glyph stream, pattern stream or any other content stream.

Note: When page processing is completed, make sure to call ElementReader.End().

Parameters
content_stream - A stream object representing the content stream (usually a Form XObject).

public void begin (Obj content_stream, Obj resource_dict)

Begin processing given content stream. The content stream may be a Form XObject, Type3 glyph stream, pattern stream or any other content stream.

Note: When page processing is completed, make sure to call ElementReader.End().

Parameters
content_stream - A stream object representing the content stream (usually a Form XObject).
resource_dict - An optional '/Resource' dictionary parameter. If content stream refers to named resources that are not present in the local Resource dictionary, the names are looked up in the supplied resource dictionary.

public void begin (Page page)

Begin processing a page.

Note: When page processing is completed, make sure to call ElementReader.End().

Parameters
page the page to start processing.

public void begin (Obj content_stream, Obj resource_dict, Context ctx)

Begin processing given content stream. The content stream may be a Form XObject, Type3 glyph stream, pattern stream or any other content stream.

Note: When page processing is completed, make sure to call ElementReader.End().

Parameters
content_stream - A stream object representing the content stream (usually a Form XObject).
resource_dict - An optional '/Resource' dictionary parameter. If content stream refers to named resources that are not present in the local Resource dictionary, the names are looked up in the supplied resource dictionary.
ctx The Optional Content (OC) Context that should be used when processing the page. Element::IsOCVisible() will return 'true' or 'false' depending on the visibility of the current Optional Content Group (OCG) and the states of flags in the given context.

public void begin (Page page, Context ctx)

Begin processing a page.

Note: When page processing is completed, make sure to call ElementReader.End().

Parameters
page the page to start processing.
ctx the Optional Content (OC) Context that should be used when processing the page. Element::IsOCVisible() will return 'true' or 'false' depending on the visibility of the current Optional Content Group (OCG) and the states of flags in the given context

public void clearChangeList ()

Clear the list containing identifiers of modified graphics state attributes. The list of modified attributes is then accumulated during a subsequent call(s) to ElementReader.Next().

public Element current ()

get current page element

Note: Every call to ElementReader::Next() destroys the current Element. Therefore, an Element becomes invalid after subsequent ElementReader::Next() operation.

Returns
  • the current Element or a 'NULL' Element. The current element is the one returned in the last call to Next().

public void destroy ()

Frees the native memory of the object. This can be explicity called to control the deallocation of native memory and avoid situations where the garbage collector does not free the object in a timely manner.

public boolean end ()

Close the current display list. If the current display list is a sub-list created using FormBegin(), PatternBegin(), or Type3FontBegin() methods, the function will end the sub-list and will return processing to the parent display list at the point where it left off before entering the sub-list.

Returns
  • true if the closed display list is a sub-list or false if it is a root display list.

public void formBegin ()

When the current element is a form XObject you have the option to skip form processing (by not calling FormBegin()) or to open the form stream and continue Element traversal into the form. To open a form XObject display list use FormBegin() method. The Next() returned Element will be the first Element in the form XObject display list. Subsequent calls to Next() will traverse form's display list until NULL is returned. At any point you can close the form sub-list using ElementReader::End() method. After the form display list is closed (using End()) the processing will return to the parent display list at the point where it left off before entering the form XObject.

public GSChangesIterator getChangesIterator ()

Get the changes iterator.

Returns
  • an iterator to the beginning of the list containing identifiers of modified graphics state attributes since the last call to ClearChangeList(). The list can be consulted to determine which graphics states were modified between two Elements. Attributes are ordered in the same way as they are set in the content stream. Duplicate attributes are eliminated.

public Obj getColorSpace (String name)

Get the color space.

Parameters
name the name of the color space
Returns
  • the specified color space
See Also

public Obj getExtGState (String name)

Get the ext GState.

Parameters
name the GState name
Returns
  • the ext GState
See Also

public Obj getFont (String name)

Get the specified font.

Parameters
name the font name
Returns
  • SDF/Cos object matching the specified name in the current resource dictionary. For 'Page' the name is looked up in the page's /Resources/<Class> dictionary. For Form XObjects, Patterns, and Type3 fonts that have a content stream within page content stream the specified resource is first looked-up in the resource dictionary of the inner stream. If the resource is not found, the name is looked up in the outer content stream's resource dictionary. The function returns NULL if the resource was not found.

public Obj getPattern (String name)

Get the pattern.

Parameters
name the pattern name
Returns
  • the specified pattern
See Also

public Obj getShading (String name)

Get the specified shading object.

Parameters
name the name of the shading object
Returns
  • the shading object
See Also

public Obj getXObject (String name)

Get the specified XObject.

Parameters
name the name of the XObject
Returns
  • the specified XObject
See Also

public boolean isChanged (int gstate_attrib)

Checks if given GState attribute is changed.

Parameters
gstate_attrib the given GState attribute
Returns
  • true if given GState attribute was changed since the last call to ClearChangeList().

public Element next ()

Get next page element

Note: Every call to ElementReader::Next() destroys the current Element. Therefore, an Element becomes invalid after subsequent ElementReader::Next() operation.

Returns
  • a page Element or a 'NULL' element if the end of current-display list was reached. You may use GetType() to determine the type of the returned Element.

public void patternBegin (boolean fill_pattern, boolean reset_ctm_tfm)

A method used to spawn the sub-display list representing the tiling pattern of the current element in the ElementReader. You can call this method at any point as long as the current element is valid.

Parameters
fill_pattern If true, the filling pattern of the current element will be spawned; otherwise, the stroking pattern of the current element will be spawned. Note that the graphics state will be inherited from the parent content stream (the content stream in which the pattern is defined as a resource) automatically.
reset_ctm_tfm An optional parameter used to indicate whether the pattern's display list should set its initial CTM and transformation matrices to identity matrix. In general, we should leave it to be false. To open a tiling pattern sub-display list use PatternBegin() method. The Next() returned Element will be the first Element in the pattern display list. Subsequent calls to Next() will traverse pattern's display list until NULL is encountered. At any point you can close the pattern sub-list using ElementReader::End() method. After the pattern display list is closed, the processing will return to the parent display list at the point where pattern display list was spawned.

public void patternBegin (boolean fill_pattern)

Pattern begin.

Parameters
fill_pattern If true, the filling pattern of the current element will be spawned; otherwise, the stroking pattern of the current element will be spawned. Note that the graphics state will be inherited from the parent content stream (the content stream in which the pattern is defined as a resource) automatically.

public void type3FontBegin (CharData char_data, Obj resource_dict)

A method used to spawn a sub-display list representing a Type3 Font glyph. You can call this method at any point as long as the current element in the ElementReader is a text element whose font type is type 3.

Parameters
char_data The information about the glyph to process. You can get this information by dereferencing a CharIterator.
resource_dict - An optional '/Resource' dictionary parameter. If any glyph descriptions refer to named resources but Font Resource dictionary is absent, the names are looked up in the supplied resource dictionary. To open a Type3 font sub-display list use Type3FontBegin() method. The Next() returned Element will be the first Element in the glyph's display list. Subsequent calls to Next() will traverse glyph's display list until NULL is returned. At any point you can close the glyph sub-list using ElementReader::End() method. After the glyph display list is closed, the processing will return to the parent display list at the point where glyph display list was spawned.

public void type3FontBegin (CharData char_data)

pawn a sub-display list representing a Type3 Font glyph.

Protected Methods

protected void clearList ()

Clear list.

protected void finalize ()

Throws
Throwable